In my above-identified copending applications I have disclosed various structures defining the discharge gap at the bottom of the applicator housing. According to application Ser. No. 320,739. the gap is formed between two sealing strips weighted down by two parallel rods attracted downwardly by a magnetic force. Application Ser. No. 364,560 discloses an applicator housing with a downwardly convex bottom member of elastic material having an axially extending slot, this slot being spanned by transverse pins, wires or other substantially inextensible reinforcing means secured to the housing bottom and leaving clearances for the passage of the printing liquid. In application Ser. No. 376,714 I have divulged an arrangement wherein the bottom of the downwardly open applicator housing is spanned by two perforated layers separately fastened to the housing wall, specifically a rubber diaphragm and a metal foil.